Leptin-stimulated endothelial nitric-oxide synthase via an adenosine 5'-monophosphate-activated protein kinase/Akt signaling pathway is attenuated by interaction with C-reactive protein

Cristina Procopio, Francesco Andreozzi, Emanuela Laratta, Angela Cassese, Francesco Beguinot, Franco Arturi, Marta Letizia Hribal, Francesco Perticone, Giorgio Sesti
Endocrinology 2009, 150 (8): 3584-93
The AMP-activated protein kinase (AMPK) lies upstream of Akt in the pathway leading to endothelial NO synthase (eNOS) activation. Whether leptin promotes eNOS activation via AMPK-dependent activation of Akt, and which of the two AMPKalpha catalytic subunits is involved, remains unknown. Leptin resistance may be partly attributed to interaction between leptin and C-reactive protein (CRP). We hypothesized that leptin effect on eNOS activation in human aortic endothelial cells might be blunted by direct interaction with human recombinant CRP. Small interfering RNAs (siRNAs) were used to knock down expression of alpha1- or alpha2-AMPK in transient transfection assay to evaluate which is involved in this pathway and whether leptin effect on eNOS activation in human aortic endothelial cells might be blunted by direct interaction with human CRP. siRNA-mediated down-regulation of AMPKalpha1, but not AMPKalpha2, abolished leptin-induced Akt-Ser(473) phosphorylation, eNOS-Ser(1177) phosphorylation, eNOS activation, and cGMP accumulation. By contrast, siRNA-mediated knockdown of Akt1 did not affect AMPKalpha1 phosphorylation, but it abolished leptin-induced phosphorylation of Akt-Ser(473) and eNOS-Ser(1177), suggesting that Akt functions downstream of AMPKalpha1. Preincubation of leptin with human recombinant CRP impaired leptin-induced AMPK activation, eNOS-Ser(1177) phosphorylation, eNOS activity, and intracellular cGMP accumulation. The data are consistent with a model implicating an AMPKalpha1-->Akt-->eNOS pathway leading to NO production in response to leptin supporting the idea that interaction between leptin and CRP may have a role in impairing leptin effect on eNOS activation, suggesting a link between leptin resistance, low-grade inflammation, and endothelial dysfunction.

Full Text Links

Find Full Text Links for this Article


You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read

Save your favorite articles in one place with a free QxMD account.


Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"